Set UDP packet site limit as recommended by https://www.dnsflagday.net/2020//#dns-flag-day-2020

VERSION

-0.5.6
+0.5.7

dns_utils.go

@@ -51,8 +51,8 @@ func NameserverHasChallenge(nameserver, fqdn, challenge string) bool {
 	// build request
 	var msg dns.Msg
 	msg.SetQuestion(dns.CanonicalName(challengeName), dns.TypeTXT)
-	// Raise MTU limit from 512 to 4096 which is the default used by dig.
-	msg.SetEdns0(4096, false)
+	// Set packet size limit as recommended by https://www.dnsflagday.net/2020//#dns-flag-day-2020
+	msg.SetEdns0(1232, false)
 
 	// request all TXT records
 	TXTAnswer, _, err := client.Exchange(&msg, nameserver)